Why won't anyone answer my first question?

Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

Someone this asap for a group of students attends a basketball game. * the group buys x hot dogs at the concession stand for $2 each. * the group buys y drinks at the concession stand for $3 each. the group buys 29 items at the concession stand for a total of $70. how many hot dogs did the group buy?

Nikolas calculated the volume of the prism. his work is shown below.